The present invention relates generally to fuel caps for providing a sealed closure on a vehicle fuel tank filler neck, and particularly to a tester for field testing the leakage level of a wide variety of fuel caps. More particularly, the present invention relates to fixtures for receiving caps to be tested for leakage and connecting those caps to fuel cap leakage tester apparatus.
In-Use Maintenance (I/M regulations enforced in many states require the inspection, diagnosis, and repair of fuel system liquid and vapor leaks as part of yearly vehicle testing. More specifically, the testing requirement is included in the I/M 240 regulation. A tester for determining whether a fuel cap for providing a sealed closure on a vehicle fuel tank filler neck leaks at a rate that is equal to or less than a specified maximum acceptable fuel cap leak rate is disclosed in PCT/US96/13415, entitled "Fuel Cap Leakage Tester," to Robert S. Harris, filed on August 16, 1996.
Fuel caps are configured to be coupled to filler necks in many different ways so as to provide a sealed closure for the open mouth of a tank filler neck. Cam-on fuel caps include cam lugs or bayonet-type lugs for engaging filler neck flanges and threaded fuel caps includes external threads for engaging internal filler neck threads. The lugs and threads operate to retain a fuel cap in a fully tightened position closing the open mouth of a filler neck.
Fuel caps come in a wide variety of shapes and sizes and the cam lugs and external threads provided on fuel caps also come in a wide variety of shapes and sizes. These cap, lug, and thread styles vary by vehicle model and model year.
What is needed is a support fixture that can receive a fuel cap during an inspection conducted using a cap-pressurizing fuel cap leakage tester to determine whether the fuel cap passes a pressure-based fuel cap leakage test. Inspectors would welcome a support fixture that is adaptable readily in the field to accept more than one style of fuel cap so that fuel caps associated with a wide variety of vehicle models and model years can be tested quickly and easily using a single fuel cap leakage tester.
According to the present invention, a fuel cap tester comprises a test base connectable to a source of pressurized air and a cap adapter connectable to the test base. The test base is formed to include a base chamber and a pressurized air supply conduit in communication with the base chamber. The cap adapter connects to the test base at one end and retains a fuel cap to be tested at another end to place the fuel cap in communication with pressurized air passed into the base chamber through the pressurized air supply conduit.
In preferred embodiments, the fuel cap tester further comprises a test unit including a housing containing a source of pressurized air and a flow connector coupling the source of pressurized air to the pressurized air supply conduit that is coupled to the base chamber in the test base to supply pressurized air to the base chamber during a fuel cap leakage test. A mechanism is provided in the test unit for comparing air pressure leakage from the base chamber in the test base past a fuel cap coupled to the test base (directly or via the cap adapter) to determine if the leakage of the cap is equal to or different from a maximum acceptable leak rate.
In preferred embodiments, the cap adapter includes a tubular member formed to include a cap-receiving chamber, a flange around the tubular member, and an O-ring seal around the tubular member adjacent to the flange. The tubular member includes an axially inner end and an axially outer end. The tubular member further includes an inner portion positioned to lie between the axially inner end and the O-ring seal and sized to fit in the base chamber formed in the test base.
The cap adapter couples a fuel cap to be tested to the test base. A base connector on the inner portion of the tubular member couples the cap-receiving chamber in the cap adapter in fluid communication with the base chamber in the test base. A fuel cap connector on the axially outer end of the tubular member retains a fuel cap to be tested in the cap-receiving chamber in the cap adapter.
In other preferred embodiments, a fuel cap tester kit comprises a test base and at least two cap adapters. A first of the cap adapters is configured to retain a first style of fuel cap in a mounted position on the first cap adapter. A second of the cap adapters is configured to retain a second style of fuel cap different from the first style of fuel cap in a mounted position on the second cap adapter. Additional cap adapters configured to retain additional styles of fuel caps can be included in the fuel cap tester kit to facilitate coupling a wide variety of fuel cap styles to the test base.
To test the leakage rate of a fuel cap to be tested, a technician first selects a cap adapter configured to retain the fuel cap to be tested from among the available cap adapters, couples the cap adapter to a test base, and couples the fuel cap to be tested to the cap adapter. The technician then uses the fuel cap leakage tester to supply pressurized air to the cap adapter through the test base and measures a leakage rate of pressurized air from the cap adapter past the fuel cap to be tested that is coupled to the cap adapter. If the measured leakage rate is less than a predetermined acceptable rate, then the fuel cap passes the leakage test. However, if the measured leakage rate is greater than the predetermined acceptable rate, then the fuel cap fails the leakage test.
Another aspect of the present invention is the test base itself The test base includes internal threads in its base chamber for mating with a wide variety of threaded fuel caps. In a presently preferred embodiment the profile, pitch, and diameter of these internal threads is defined to fit nearly all common fuel cap thread profiles.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.